Various analytical instruments exist for analyzing properties or characteristics of a material by exposing a specimen or sample of the material to electromagnetic (EM) energy and detecting a response of the specimen or sample to the exposure. For example, light of one or more particular wavelengths and luminous intensities may be emitted into the specimen and an amount of light transmitted through or an amount of light absorbed by the specimen may be measured. As various materials will absorb some wavelengths while reflecting others, various properties of the specimen may be determined by measuring EM energy transmittance and absorbance by the specimen. Furthermore, some materials may exhibit a response known as fluorescence during which the material may actually emit EM energy at a different or shifted wavelength to that which the material is exposed. These spectral responses, among others, may be used to determine properties or characteristics of the material.
The ability to control the optical path length of the specimen may have a considerable effect on the accuracy of analytical results. In particular, the percent of EM energy that is transmitted through a material depends at least partially on the optical path length, e.g. the distance that the EM energy travels through the material. For example, a material may transmit fifty percent of the EM energy of a particular wavelength over an optical path length of 0.2 centimeters (cm) while transmitting only two percent of the EM energy if the optical path length is changed to 1 cm. Therefore, controlling the optical path length is of great importance in obtaining accurate measurements of a material and, resultantly, new approaches to controlling the optical path length while minimizing or eliminating associated EM energy intensity variations, which may lead to improved accuracy in analytical instruments, are desirable.